Network backup methods typically utilize file image backups and/or volume image backups. File backups backup individual files, while, a volume backup backs up all data in a specified volume. Different operating systems or file systems may treat volumes differently. For example, in a Windows-based system, a volume backup stores all files and folders of the selected volume independent of their attributes (including hidden and system files), the boot record, the file allocation table (FAT) if it exists, the root and the zero track of the hard disk with the master boot record (MBR). In a Linux-based system, a volume backup stores all files and directories of the selected volume independent of their attributes, a boot record, and the file system super block. In general, however, a volume-based backup backs up all data in a specified volume to a target storage node.
Volume image backups are popular for full and incremental backups. Volume based full and incremental backups are faster than file by file. Volume backups are especially useful in high-density file system (HDFS) environments where there are millions of files to be backed up. Incremental volume block based backup are done with the help of change block tracker (CBT) component which captures changes since the last previous backup. This approach saves time and also space because only changed blocks are backed up. However there is a growing need to backup sub file changes (i.e., changes within individual files) using CBT technique at file/volume level to obtain changes respective of a file and backup only those. This type of backup would greatly improve backup time for files which are very large in size, such as database files.
What is needed, therefore, is a backup method that provides a greater deal of granularity to volume image backups by providing backups of sub-file changes.
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